EP2673863A1

EP2673863A1 - System for charging an energy store, and method for operating the charging system

Info

Publication number: EP2673863A1
Application number: EP11802766.3A
Authority: EP
Inventors: Peter Feuerstack; Erik Weissenborn; Martin Kessler
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2011-02-09
Filing date: 2011-12-29
Publication date: 2013-12-18
Also published as: CN103339819A; WO2012107148A1; US20130320912A1; CN103339819B; DE102011003863A1

Abstract

The invention relates to a system for charging at least one energy storing cell (5) in a controllable energy store (2) that is used to control and supply electric energy to an n-phase electric machine (1), wherein n>=1. The controllable energy store (2) has n parallel energy supply branches (3-1, 3-2, 3-3), each of which has at least two serially connected energy storing modules (4), each said energy storing module comprising at least one electric energy storing cell (5) with a corresponding controllable coupling unit (6). The energy supply branches (3-1, 3-2, 3-3) can be connected to a reference bus (T-), and each energy supply branch can be connected to a phase (U, V, W) of the electric machine (1). The coupling units (6) bridge the respective corresponding energy storing cells (5) or connect same into the respective energy supply branch (3-1, 3-2; 3-3) dependent on control signals. The aim of the invention is to allow at least one energy storing cell (5) to be charged. This is achieved in that at least one external energy source (10) can be connected to an energy supply branch (3-1; 3-2; 3-3) and to the reference bus (T-).

Description

title

System for charging an energy storage and method for operating the charging system

The invention relates to a system for charging an energy store and a method for operating the charging system according to the invention.

State of the art

It is becoming apparent that in the future both stationary applications, e.g.

Wind turbines, as well as in vehicles such as hybrid or electric vehicles, increasingly electronic systems are used that combine new energy storage technologies with electric drive technology. In conventional applications, an electric machine, e.g. is designed as a rotating field machine, controlled by a converter in the form of an inverter. Characteristic of such systems is a so-called DC voltage intermediate circuit, via which an energy store, usually a battery, is connected to the DC side of the inverter. In order to meet the power and energy requirements of each application, multiple battery cells are connected in series. Since the power provided by such an energy store must flow through all the battery cells and a battery cell can only conduct a limited current, battery cells are often additionally connected in parallel in order to increase the maximum current.

The series connection of several battery cells in addition to a high total voltage involves the problem that the entire energy storage fails if a single battery cell fails, because then no battery power can flow. Such a failure of the energy storage can lead to a failure of the entire system. In a vehicle, failure of the traction battery can result in the vehicle "stalling". For other applications, such as the rotor blade adjustment of

Wind turbines, it may in unfavorable conditions, such. strong Wnd, even come to safety-threatening situations. Therefore, it is always high

To strive for reliability of energy storage, where with "reliability" the

Ability of a system is called to work for a given time error-free. In the older applications DE 10 2010 027857 and DE 10 2010 027861 batteries are described with several battery module strings, which are directly connected to an electrical machine. The battery module strands in this case have a plurality of battery modules connected in series, each battery module having at least one battery cell and an associated controllable coupling unit, which allows depending on control signals to interrupt the respective battery module strand or to bridge the respectively associated at least one battery cell or each assigned to switch at least one battery cell in the respective battery module string. By suitable control of the coupling units, for example by means of pulse width modulation, it is also possible to provide suitable phase signals for controlling the electrical machine, so that a separate one can be used

Pulse inverter can be dispensed with. The required for controlling the electrical machine pulse inverter is so to speak integrated into the battery. For purposes of disclosure, these two earlier applications are fully incorporated into the present application.

DISCLOSURE OF THE INVENTION The invention provides a system for charging at least one energy storage cell in a controllable energy store, which controls and electrical

Power supply of an n-phase electric machine, with n> 1, is used. In this case, the controllable energy store has n parallel energy supply branches, each of which has at least two energy storage modules connected in series, and which each comprise at least one electrical energy storage cell with an associated controllable coupling unit. The power supply branches are on the one hand connected to a reference rail and on the other hand, each with a phase of the electric machine. In response to control signals, the coupling units bridge the respectively assigned energy storage cells or they switch the respectively assigned energy storage cells into the respective energy supply branch. At least one external energy source is connectable on the one hand to a power supply branch and on the other hand to the reference rail.

The invention also provides a method for operating a charging system according to the invention, wherein energy storage cells are charged simultaneously in all energy supply branches. Advantages of the invention

The invention is based on the basic idea of electrically connecting the energy supply branches to an external energy source for directly charging the energy storage cells without the intermediary of an additional charge component.

In addition to the saving of additional charge components that stands out

inventive system characterized in that a simultaneous loading of

Energy storage cells in all energy supply branches, in particular even a simultaneous charging of all energy storage cells of the controllable energy storage, individually adjustable by the controllable energy storage charging currents is possible.

According to the invention, an external energy source directly with the

Energy supply branches and thus also connected to the associated phase of the electric machine. In this case, it is not necessary to provide a separate external energy source for each energy supply branch, since the individual energy supply branches are electrically connected to one another via the phases of the electrical machine and the neutral point of the electrical machine, which results in a charging current flow through all

Energy supply branches allowed.

In such an embodiment, the charging current but also flows through the

Motor inductances, which are not ideal in reality and therefore have a parasitic resistive component, which impedes the flow of current. In order to circumvent this problem, it is also possible to provide n external energy sources, which can be connected on the one hand to a respective power supply branch and on the other hand to the reference rail. In this case, a separate energy source is available for each energy supply branch, which can feed a charging current without detour via the electrical machine directly into the respective energy supply branch. According to one embodiment of the invention, the external energy sources are as

Power sources designed, which offers the advantage that they can be connected in parallel to the acting as a voltage source controllable energy storage without further action, since the charging current is automatically limited by the power sources.

Alternatively, the energy sources can also be configured as voltage sources whose voltage values are below the voltages of the respectively connected ones Energy supply branches lie. However, this results in the problem that the charging current is not automatically limited by the voltage sources, so that they are not readily parallel to the controllable acting as a voltage source

Energy storage can be switched. However, this problem is solved by the fact that the energy sources each comprise, in addition to the voltage sources, series-connected additional charging inductances which can be operated in conjunction with the coupling units of the controllable energy store as a step-up converter. In conjunction with a step-up converter, however, the voltage sources gain "current source character", so that even when using voltage sources as external energy storage no additional charging components are required.

According to one embodiment of the invention, the energy sources which can be connected to the energy supply branches of the controllable energy store are designed as DC voltage sources or DC sources. However, if the coupling units of the controllable energy store are designed as full bridges, then the

Alternatively, energy sources may be designed as symmetrical AC voltage sources or AC sources.

In coupling units in the form of full bridges, the energy sources can also be configured as asymmetrical AC voltage sources or AC sources. In order to avoid unwanted moments during the charging process, however, controllable switching elements are provided in this case, by means of which the electric machine can be separated from the power supply branches. Alternatively or additionally, unwanted moments during the charging process can be avoided by mechanically blocking the electric machine during the charging process, e.g. with the help of a transmission pawl. Alternatively, the rotor position of the electric machine can also be monitored, e.g. be switched off by means of a corresponding sensor, and in the case of a detected rotor movement.

Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings.

Brief description of the drawings Show it:

Fig. 1 is a schematic representation of a first embodiment

Charging system according to the invention,

Fig. 2 is a schematic representation of a second embodiment

loading system according to the invention in a loading phase,

Fig. 3 shows the charging system of FIG. 2 in a freewheeling phase.

Embodiments of the invention

Figures 1 to 3 show schematic representations of embodiments of a charging system according to the invention. To a three-phase electric machine 1, a controllable energy storage 2 is connected. The controllable energy store 2 comprises three power supply branches 3-1, 3-2 and 3-3, which on the one hand with a reference potential T- (reference rail), which leads in the illustrated embodiments, a low potential, and on the other hand in each case with individual phases U, V, W of the electric machine 1 are connected. Each of the power supply branches 3-1, 3-2 and 3-3 has m series-connected energy storage modules 4-1 1 to 4-1m and 4-21 to 4-2m and 4-31 to 4-3m, respectively 2. The energy storage modules 4, in turn, each comprise a plurality of electrical energy storage cells connected in series, which for reasons of clarity are only provided in the energy supply branch 3-3 connected to the phase W of the electric machine 1 with reference symbols 5-31 to 5-3m. The energy storage modules 4 further comprise one each

Coupling unit, which is associated with the energy storage cells 5 of the respective energy storage module 4. For reasons of clarity, the coupling units are also provided only in the power supply branch 3-3 with reference numerals 6-31 to 6-3m. In the illustrated embodiments, the coupling units 6 are each formed by four controllable switching elements 7-31 1, 7-312, 7-313 and 7-314 to 7-3m1, 7- 3m2, 7-3m3 and 7-3m4, which in shape a full bridge are connected. The switching elements can be embodied as power semiconductor switches, for example in the form of IGBTs (Insulated Gate Bipolar Transistors) or as MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors). The coupling units 6 make it possible to interrupt the respective power supply branch 3 by opening all switching elements 7 of a coupling unit 6.

Alternatively, the energy storage cells 5 can either be bridged by closing two of the switching elements 7 of a coupling unit 6, e.g.

Close the switches 7-312 and 7-314 or in the respective

Power supply branch 3 are switched, for. Close the switches 7-312 and 7-313.

The total output voltages of the power supply branches 3-1 to 3-3 are determined by the respective switching state of the controllable

Switching elements 7 of the coupling units 6 and can be adjusted in stages. The grading results depending on the voltage of the individual

Energy storage modules 4. If one starts from the preferred embodiment of similarly designed energy storage modules 4, the result is a maximum possible total output voltage from the voltage of a single one

Energy storage module 4 times the number m of per energy supply branch 3 in series energy storage modules. 4

The coupling units 6 thus allow the phases U, V, W of the electric machine 1 either against a high reference potential or a low

Switching reference potential and can thus fulfill the function of a known inverter. Thus, the power and operating mode of the electric machine 1 can be controlled by the controllable energy store 2 with suitable control of the coupling units 6. The controllable

Energy storage 2 thus fulfills a dual function insofar as it serves on the one hand the electrical power supply on the other hand, but also the control of the electric machine 1.

The electric machine 1 has stator windings 8-U, 8-V and 8-W, which are connected in a known manner in star connection with each other.

The electric machine 1 is designed as a three-phase three-phase machine in the illustrated embodiments, but may also have fewer or more than three phases. Of course, the number of power supply branches 3 in the controllable energy store 2 also depends on the number of phases of the electrical machine. In the exemplary embodiments illustrated, each energy storage module 4 in each case has a plurality of energy storage cells 5 connected in series. The

Energy storage modules 4 but can alternatively also only a single

Energy storage cell or parallel energy storage cells

exhibit.

In the illustrated embodiments, the coupling units 6 are each formed by four controllable switching elements 7 in the form of a full bridge, which also offers the possibility of a voltage reversal at the output of the energy storage module .. The coupling units 6 but can also be more or less

controllable switching elements be realized as long as the necessary functions

(Bridging the power supply cells and switching the

Energy supply cells in the power supply branch) can be realized.

In particular, the coupling units can also be in the form of Hall bridges

be educated. Such embodiments are shown by way of example in the older applications DE 10 2010 027857 and DE 10 2010 027861.

To the charge of energy storage cells 5 one or more

Enabling energy storage modules 4, three as power sources 10'-1, 10'-2 and 10'- 3 configured external energy sources 10-1 or 10-2 or 10-3 are provided, which on the one hand with a respective energy supply branch 3-1 or 3-2 or 3-3 and on the other hand with the reference rail T- are connected. The current sources 10 'can be used as DC sources or in the illustrated embodiment of

Coupling units 6 are designed as full bridges as well as AC sources and each provide a suitable charging of the energy storage cells 5 in the corresponding power supply branch 3 charging current. Since the individual power supply branches 3-1 to 3-3 are connected to each other via the star point S of the electric machine 1, it is also conceivable as an alternative to the embodiment shown not to provide a separate power source 10 'for each of the power supply branches 3, but only a part the power supply branches 3 to a power source 10 'to connect.

Figures 2 and 3 show a second embodiment of the invention. This differs from the third embodiment in that the external

Energy sources 10-1, 10-2 and 10-3 not as power sources, but as

Voltage sources 10 "-1, 10" -2 and 10 "-3 are configured whose voltage values are below the voltages of the power supply branches 3-1 to 3-3 each of the power sources 10-1, 10-2 and 10-3 has one in series with the

Voltage source 10 "-1 or 10" -2 or 10 "-3 switched additional charging inductance 1 1- 1 or 1 1-2 or 1-3, the voltage sources 10" can as

DC sources or be executed in the illustrated embodiment of the coupling units 6 as full bridges as AC sources. In order to be able to provide a charge current suitable for charging the energy storage cells 5 even in the case of the voltage source 10 ", the charging process must take place in two phases, which in the following exemplifies the charging process of the energy storage cells 5 of a single energy storage module 4, namely the energy storage cells 5 -3m of the energy storage module 4-3m in the power supply branch 3-3, using a designed as a DC voltage source voltage source 10 "is described. The coupling units 6 are operated in conjunction with the additional charging inductors 11 as a boost converter. During a charging phase, which is shown in FIG. 2, the coupling units 6-31 to 6-3m of the energy storage modules 4-31 to 4-3m, which in the

Energieversorgungszweig 3-3 lie, in which also to be loaded

Energy storage cells 5-31 are controlled by a control unit, not shown in such a way that the respective associated energy storage cells are 5-31 to 5-3m bridged. Concretely, this is achieved by closing the switching elements 7-312 and 7-314 to 7-3m2 and 7-3m4, whereas the switching elements 7-311 and 7-313 to 7-3m1 and 7-3m3 are opened. All other coupling units 6, that is, all coupling units 6 in the energy storage modules 4 of the other two

Power supply branches 3-1 and 3-2 are controlled such that the respective power supply branches 3-1 and 3-2 are interrupted. Specifically, this is achieved in that each switching elements 7 of the coupling units 6 are opened.

Such a control of the coupling units 6 causes a current flow through the charging inductor 1-3, so that during the charging phase electrical energy in the

Charging inductance 1 1-3 is stored.

In a free-wheeling phase following the charging phase, which is shown in FIG. 3, the coupling unit 6-3m, which is assigned to the energy storage cells 5-3m to be charged, is controlled in such a way that the associated energy storage cells 5-3m in the

Power supply branch 3-3 are switched. This is achieved concretely in that the switching elements 7-3m2 and 7-3m3 are opened and the switching elements 7-3m1 and 7 3m4 to be closed. All other coupling units 6-31 to 6-3 (m-1), which lie in the power supply branch 3-3 of the energy storage cells 5-3m to be charged, but which are not assigned to any energy storage cells 5 to be charged, are controlled in such a way that the respective associated energy storage cells 5-31 to 5-3 (m-1) are bridged (closing of the switching elements 7-312 and 7-314 to 7-3 (m-1) 2 to 7- 3 (m-1) 4 and opening the Switching elements 7-311 and 7-313 to 7-3 (m-1) 1 to 7-3 (m-1) 3. The coupling units 6-1 1 to 6-1 m and 6-21 to 6-2m in the other

Power supply branches 3-1 and 3-2 are further controlled so that the respective power supply branches 3-1 and 3-2 are interrupted.

Such a control of the coupling units 6 causes an electrical connection of the charging inductor 1-3 with the energy storage cells 5-3m to be charged. The

Charging inductance 1 1-3 drives the current and charges in this way the

Energy storage cells 5-3m up.

In principle, all energy storage cells 5 in all energy supply branches 3 of the controllable energy store 2 can be charged in the manner described. With the system according to the invention but it is also possible by appropriate control of the coupling units 6, a plurality of energy storage cells 5 in several

Energieversorgungszweigen 3 or even all energy storage cells 5 to load simultaneously. A distribution of a current supplied by the power source 10 to the individual power supply branches 3 is on the voltages of the

Power supply branches 3 adjustable. The voltages of the power supply branches 3 are in turn by the number of in the respective

Energy supply branch 3 switched energy storage cells 5 set.

Also in the embodiment explained with reference to FIGS. 2 and 3, it is conceivable, as an alternative to the illustrated variant, not to provide a separate voltage source 10 "for each of the energy supply branches 3, but only a part of the

To connect power supply branches 3 with a voltage source 10 '. Here, too, it makes use of the fact that the individual energy supply branches 3-1 to 3-3 are connected to each other via the star point S of the electric machine 1 anyway.

If, in the case of direct coupling of energy sources 10 to the energy supply branches 3 of the controllable energy store 2, asymmetrical AC voltage sources, such as the public grid, are used, this can lead to the generation of undesirable moments to come in the electric machine. Therefore, not shown controllable switching elements may be provided, which allow to separate the electric machine 1 during the charging of the power supply branches. Alternatively or additionally, unwanted moments during the charging process can also be avoided by mechanically blocking the electric machine 1 during the charging process, for example by means of a transmission pawl.

Alternatively, the rotor position of the electric machine 1 can be monitored, e.g. be switched off by means of a corresponding sensor, and in the case of a detected rotor movement.

Claims

Claims 1. A system for charging at least one energy storage cell (5) in a controllable energy store (2), which serves the control and the electrical power supply of an n-phase electric machine (1), where n> 1, wherein

- The controllable energy storage (2) n parallel power supply branches (3-1, 3-2, 3- 3), which

Each have at least two energy storage modules (4) connected in series, which each comprise at least one electrical energy storage cell (5) with an associated controllable coupling unit (6),

^■ on the one hand with a reference rail (T) are connectable and

^■ on the other hand with a respective phase (U, V, W) of the electrical machine (1) are connectable,

- The coupling units (6) in response to control signals, the respective associated energy storage cells (5) bridge or the respectively associated

Switch energy storage cells (5) in the respective power supply branch (3-1, 3-2, 3-3),

- At least one external energy source (10), which on the one hand with a

Power supply branch (3-1, 3-2, 3-3) and on the other hand with the reference rail (T-) is connectable.

2. System according to claim 1, wherein n external energy sources (10-1, 10-2, 10-3) are provided which on the one hand with a respective energy supply branch (3-1, 3-2, 3-3) and on the other hand with the Reference rail (T) are connectable.

3. System according to any one of claims 1 or 2, wherein the energy sources (10) as

Power sources (10 ') are configured.

4. System according to any one of claims 1 or 2, wherein the external energy sources (10) voltage sources (10 ") with each connected in series additional

Charging inductances (1 1), wherein voltage values of the voltage sources (10 ") are below the voltages of the respective connected power supply branch (3-1; 3- 2; 3-3), and wherein the coupling units (6) in conjunction with the additional charging inductances (11) are operable as a boost converter.

5. System according to one of claims 1 to 4, wherein the energy sources (10) as

DC sources (10 ') and DC voltage sources (10 ") are configured.

6. System according to one of claims 1 to 4, wherein the energy sources (10) as symmetrical AC sources (10 ') or AC voltage sources (10 ") and the coupling units (6) are designed as full bridges.

7. System according to one of claims 1 to 4, wherein the energy sources (10) as asymmetrical AC sources (10 ') and AC sources (10 ") and the coupling units (6) are designed as full bridges and wherein the electric machine (1) controllable switching elements of the power supply branches (3-1, 3-2, 3-3) is separable.

8. A method for operating a charging system according to any one of claims 1 to 7, wherein energy storage cells (5) in all power supply branches (3-1, 3-2, 3-3) are loaded simultaneously.